This report documents the conceptual Managed Aquifer Recharge (MAR) and groundwater resource targets identified from initial analysis of airborne electromagnetics (AEM) data acquired during Phase 2 of the Broken Hill Managed Aquifer Recharge (BHMAR) Project (Lawrie, 2009; Lawrie et al., 2008a, 2009a, b; Figure 1). The BHMAR Phase 2 study builds on an earlier scoping study (Lewis et al., 2008) and Phase 1 technical risk assessment (Lawrie et al, 2009a, b), and is part of the Australian Government's plan to secure Broken Hill's water supply and allow for significant amounts of water currently stored at Menindee Lakes to be returned to the environment. The Australian Government has committed up to $400 million to the project, which is managed through the Australian Government Department of the Environment, Water, Heritage and the Arts (DEWHA).

A detailed analysis of aquifer systems in the Broken Hill Managed Aquifer Recharge priority areas has clarified our understanding of key components of the aquifer systems. Of the priority areas examined in detail, the aquifers located in the Darling Floodplain are considered to have the greatest potential for developing Managed Aquifer Recharge (MAR) options and for hosting significant volumes of previously undefined fresh and brackish groundwaters with low levels of allocation, thereby assisting the larger strategic effort aimed at identifying significant water-saving measures for the Darling River system.

Conceptual MAR targets in the Broken Hill region were identified in previous investigations (Lewis et al., 2008; Lawrie et al., 2009a). In the BHMAR Phase 2 study, the project team is required to make recommendations on the presence and suitability of potential MAR sites with an 80% confidence level. While this will be attempted through a combination of AEM, borehole analysis and seismic reflection data acquisition, AEM is the prime dataset required to map the aquifer targets in 3D.

In the course of a study to examine the depths to various regolith layers in the North Arunta area, anomalous geochemistry values where noticed in an area of particularly dense drilling. Company reports were obtained to further examine the area investigate if a prospect had been identified. A detailed magnetic survey (100 m line spacing) of the area was also revealed. With the aid of the company reports and data geology and mineralisation of the Abrolhos prospects have been investigated.

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The Murray Canyons area of interest extends across a series of two major Mesozoic basins (Otway and Bight), remnants of a thin Permian basin (Troubridge), and broad areas of thin Cainozoic cover over continental crust (Encounter Bay Shelf) and oceanic crust (Australia-Antarctica Basin). It has been possible to classify and map a range of different levels of petroleum prospectivity in this area by using a risking scheme that assesses the likelihood of hydrocarbon generation and migration, sealed reservoirs, and valid traps. The level of knowledge and confidence in the risk assessment is also incorporated into the ranking of petroleum prospectivity. Using this approach, its is possible to identify areas that are likely to be explored for petroleum accumulations. These include one proven prospective area (Outer Crayfish), four indicated prospective areas (East Ceduna, East Duntroon, Inner Crayfish and Morum Sub-basin 1), and one area with inferred prospectivity (Morum Sub-basin 2). The Murray Canyons area of interest also includes eight areas which are considered a high risk for the presence of petroleum accumulations, and are thus less likely to be explored (Trumpet Shelf, Couedic, Recherche-Hunter, Otway Thin Outer Cretaceous, Murray Canyons, Troubridge 1, Troubridge 2, and Encounter Bay Shelf). Two non-prospective areas are present where hydrocarbons accumulations are considered to be absent, and are unlikely to be explored (Otway Volcanic Buildup and Abyssal Plain).

The Nelson, Zeehan and Apollo regions are three of eleven Broad Areas of Interest identified as possible areas for the establishment of Marine Protected Areas by Environment Australia (with statutory and policy responsibility for MPAs), the National Oceans Office (with responsibility for regional marine plans) and other stakeholders. An assessment of the petroleum prospectivity of the Nelson, Zeehan and Apollo regions was undertaken by Geoscience Australia in order to identify areas with the potential to generate and host hydrocarbon accumulations. The assessment used a risk-based approach whereby factors that controlled the sourcing and trapping of hydrocarbons were assessed based on the likeihood of their presence or absence within a particular region. The level of knowledge and confidence in the risk assessment was also incorporated into the ranking of petroleum prospectivity. These factors were considered along with other geological risks to formulate a classification scheme. This scheme has been applied to Nelson 1B, Zeehan 1C and Apollo 1D BAOIs.

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